It means "clown" in the language Assamese/Asamiya spoken in
Assam, India.
It is a rather popular slang in Bangladesh/
Bengal due to certain racially questionable comedy plays namely
Shong Bhong Chong (2009).
random bengali boomer: hey
shreshtha have you watched
Shong Bhong Chong in the local theatre airing this weekend?
random bengali boomer whamen: yes i have,
shong was a complete clown
Chakma fuck!